1. Field of the Invention
The present invention relates to an anode containing at least one of silicon (Si) and tin (Sn) as an element and a battery using the anode.
2. Description of the Related Art
In recent years, as mobile devices have been sophisticated and multi-functionalized, the higher capacity of secondary batteries as a power source for these mobile devices has been demanded. As a secondary battery to meet such a demand, there is a lithium ion secondary battery. However, since graphite is used for the anode in the lithium ion secondary battery in practical use currently, the battery capacity thereof is in a saturated state and thus it is difficult to attain a vastly high capacity thereof. Therefore, it is considered to use silicon, tin or the like for the anode. In recent years, forming an anode active material layer on an anode current collector by vapor-phase deposition method or the like has been reported (for example, refer to Japanese Unexamined Patent Application Publication Nos. 8-50922 and 11-135115, and Japanese Patent Publication No. 2948205).
However, silicon or tin is largely expanded and shrunk due to charge and discharge. Thus, there has been disadvantages as follows. That is, for example, the anode active material layer is dropped, and the cycle characteristics are lowered. Further, the anode current collector is deformed and the wrinkles are generated in the anode, and thus the battery is swollen. Therefore, it is considered that by forming a groove in the anode active material layer or by forming a slit in the anode current collector, the stress due to the expansion and shrinkage is relaxed and the characteristics are improved (for example, refer to Japanese Unexamined Patent Application Publication Nos. 2003-17040 and 2003-17069).